§29.33 Main rotor speed and pitch limits

(a) Main rotor speed limits. A range of m ain rotor speeds must be established that: (1) With power on, provi des adequat e margin to accommodate the variations in rotor speed occurri ng i n any appropri ate manoeuvre, and i s consi stent wi th t he kind of governor or synchroniser used; and (2) With power off, allows each appropriate aut orotative m anoeuvre to be performed throughout t he ranges of ai rspeed and weight for which certification is requested. (b) Normal main rotor high pitch limit (power-on). For rotorcraft, except helicopters required to have a m ain rotor low speed warning under sub-paragraph (e), it m ust be shown, wi th power on and without ex ceeding approved engine maximum limitations, that m ain ro tor sp eeds substantially less th an th e m inimum ap proved main rotor speed will not occur under any sustained flight condition. This must be met by: (1) Appropriate setting of t he m ain rotor high pitch stop; (2) Inherent rotorcraft characteristics that m ake unsafe low m ain rotor speeds unlikely; or (3) Adequate means to warn the pilot of unsafe main rotor speeds. (c) Normal main rotor low pitch limit (power-off). It must be shown, wi th power off, that: (1) The normal main ro tor lo w p itch limit p rovides su fficient ro tor speed, in any autorotative condition, under the m ost critical combinations of weight and airspeed; and (2) It is possible to prevent overspeeding of t he rot or wi thout except ional piloting skill. (d) Emergency high pitch. If the m ain rotor high pitch stop is set to meet sub-paragraph (b)(1), and if that stop cannot be exceeded inadvertently, additional pi tch m ay be made available for emergency use. (e) Main rotor low speed warning for helicopters. For each single engine helicopter, and each multi-engine helicopter that does not have an approved device that autom atically increases power on the operating engi nes when one engi ne fails, there must be a m ain ro tor lo w sp eed warning which meets the following requirements: (1) The warning m ust be furnished to the pilot in all flig ht co nditions, in cluding power-on and power-off fl ight, when t he speed of a m ain rot or appro aches a value that can jeopardise safe flight. (2) The warning m ay be furnished either t hrough t he i nherent aerody namic qualities of the helicopter or by a device. (3) The warning m ust be clear and distinct under all conditions , and m ust be clearly distinguishable from all other warnings. A vi sual device that requires the attention of the crew within the cockpit is not acceptable by itself. (4) If a warning device is used, the device m ust autom atically deactivate and reset when the low-speed c ondition is corrected. If the device has an audi ble warning, it must also be equipped with a m eans fo r th e p ilot to manually silence the audible warning before the low-speed condition is corrected.